Methods for treating water

ABSTRACT

Disclosed is a method of providing potable water that includes providing a filter, passing water through the filter, and removing bacteria and viruses from the water with the filter. The filter comprises a housing having an inlet and an outlet and a filter material disposed within the housing, the filter material formed at least in part from a plurality of filter particles consisting of mesoporous activated carbon. A sum of mesopore and macropore volumes of the filter particles may be between about 0.2 mL/g and about 2 mL/g, wherein mesopore means an intra-particle pore having a diameter between 2 nm and 50 nm, and macropore means an intra-particle pore having a diameter greater than 50 nm, a total pore volume of the filter particles is greater than about 0.4 mL/g and less than about 3 mL/g, and a ratio of the sum of the mesopore and macropore volumes to the total pore volume of the filter particles is greater than about 0.3. The filter removes bacteria and viruses from the water at a level of Filter Bacteria Log Removal of greater than about 2 logs and a Filter Viruses Log Removal of greater than about 1 log.

CROSS REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. § 120, this application is a continuation of U.S.application Ser. No. 10/464,210, filed on Jun. 18, 2003, still pending,the substance of which is incorporated herein by reference. U.S.application Ser. No. 10/464,210 is a continuation of InternationalApplication Nos. PCT/US03/05416 and PCT/US03/05409, both of whichdesignate the U.S., both of which were filed Feb. 21, 2003, thesubstances of which are incorporated herein by reference. Additionally,U.S. application Ser. No. 10/464,210 is a continuation-in-part of U.S.application Ser. Nos. 09/935,962, and 09/935,810, both of which werefiled on Aug. 23, 2001, both now abandoned, the substances of which areincorporated herein by reference.

FIELD OF THE INVENTION

One or more exemplary embodiments are directed to methods of providingpotable water. More particularly, one or more exemplary embodiments aredirected to methods of treating untreated water with a filter to formpotable water.

BACKGROUND OF THE INVENTION

Water may contain many different kinds of contaminants including, forexample, particulates, harmful chemicals, and microbiological organisms,such as bacteria, parasites, protozoa and viruses. In a variety ofcircumstances, these contaminants should be removed before the water isused. For example, in many medical applications and in the manufactureof certain electronic components, extremely pure water should beutilized. As a more common example, any harmful contaminants should beremoved from the water before it is potable, i.e., fit to consume.Despite modern water purification means, the general population may beat risk, and in particular, infants and persons with compromised immunesystems may be at considerable risk.

In the U.S. and other developed countries, municipally treated water maytypically include one or more of the following impurities: suspendedsolids, bacteria, parasites, viruses, organic matter, heavy metals, andchlorine. Breakdown and other problems with water treatment systemssometimes can lead to incomplete removal of bacteria and viruses. Inother countries, there may be deadly consequences associated withexposure to contaminated water, as some of those countries may haveincreasing population densities, increasingly scarce water resources,and no water treatment utilities. It is sometimes common for sources ofdrinking water to be in close proximity to human and animal waste, suchthat microbiological contamination is a major health concern. As aresult of waterborne microbiological contamination, an estimated sixmillion people die each year, half of which are children under 5 yearsof age.

In 1987, the U.S. Environmental Protection Agency (EPA) introduced the“Guide Standard and Protocol for Testing Microbiological WaterPurifiers”. The protocol establishes minimum requirements regarding theperformance of drinking water treatment systems that are designed toreduce specific health related contaminants in public or private watersupplies. The requirements are that the effluent from a water supplysource exhibits 99.99% (or equivalently, 4 log) removal of viruses and99.9999% (or equivalently, 6 log) removal of bacteria against achallenge. Under the EPA protocol, in the case of viruses, the influentconcentration should be 1×10⁷ viruses per liter, and in the case ofbacteria, the influent concentration should be 1×10⁸ bacteria per liter.Because of the prevalence of Escherichia coli (E. coli, bacterium) inwater supplies, and the risks associated with its consumption, thismicroorganism is used as the bacterium in the majority of studies.Similarly, the MS-2 bacteriophage (or simply, MS-2 phage) is typicallyused as the representative microorganism for virus removal because itssize and shape (i.e., about 26 nm and icosahedral) are similar to manyviruses. Thus, a filter's ability to remove MS-2 bacteriophage maydemonstrate its ability to remove other viruses.

Due to these requirements and a general interest in improving thequality of potable water, there is a continuing desire to provideprocesses for manufacturing filter materials and filters, which arecapable of removing bacteria and/or viruses from a fluid.

SUMMARY OF THE INVENTION

One embodiment of a method of providing potable water includes providinga filter, passing water through the filter, and removing bacteria andviruses from the water with the filter. The filter comprises a housinghaving an inlet and an outlet and a filter material disposed within thehousing, the filter material formed at least in part from a plurality offilter particles consisting of mesoporous activated carbon. A sum ofmesopore and macropore volumes of the filter particles may be betweenabout 0.2 mL/g and about 2 mL/g, wherein mesopore means anintra-particle pore having a diameter between 2 nm and 50 nm, andmacropore means an intra-particle pore having a diameter greater than 50nm, a total pore volume of the filter particles is greater than about0.4 mL/g and less than about 3 mL/g, and a ratio of the sum of themesopore and macropore volumes to the total pore volume of the filterparticles is greater than about 0.3. The filter removes bacteria andviruses from the water at a level of Filter Bacteria Log Removal ofgreater than about 2 logs and a Filter Viruses Log Removal of greaterthan about 1 log.

Another embodiment of a method of providing potable water includesproviding a filter, passing water through the filter, and removingbacteria and viruses from the water with the filter. The filtercomprises a housing having an inlet and an outlet and a filter materialdisposed within the housing, the filter material formed at least in partfrom a plurality of filter particles consisting of mesoporous and basicactivated carbon. A sum of mesopore and macropore volumes of the filterparticles may be between about 0.2 mL/g and about 2 mL/g, whereinmesopore means an intra-particle pore having a diameter between 2 nm and50 nm, and macropore means an intra-particle pore having a diametergreater than 50 nm, a total pore volume of the filter particles isgreater than about 0.4 mL/g and less than about 3 mL/g, and a ratio ofthe sum of the mesopore and macropore volumes to the total pore volumeof the filter particles is greater than about 0.3. The filter removesbacteria and viruses from the water at a level of Filter Bacteria LogRemoval of greater than about 2 logs and a Filter Viruses Log Removal ofgreater than about 1 log.

Another embodiment of a method of providing potable water includesproviding a filter, passing water through the filter, and removingbacteria and viruses from the water with the filter. The filtercomprises a housing having an inlet and an outlet and a filter materialdisposed within the housing, the filter material formed at least in partfrom a plurality of filter particles consisting of mesoporous, basic andreduced oxygen activated carbon. A sum of mesopore and macropore volumesof the filter particles may be between about 0.2 mL/g and about 2 mL/g,wherein mesopore means an intra-particle pore having a diameter between2 nm and 50 nm, and macropore means an intra-particle pore having adiameter greater than 50 nm, a total pore volume of the filter particlesis greater than about 0.4 mL/g and less than about 3 mL/g, and a ratioof the sum of the mesopore and macropore volumes to the total porevolume of the filter particles is greater than about 0.3. The filterremoves bacteria and viruses from the water at a level of FilterBacteria Log Removal of greater than about 2 logs and a Filter VirusesLog Removal of greater than about 1 log.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the invention, it is believed that the presentinvention will be better understood from the following description takenin conjunction with the accompanying drawings in which:

FIG. 1 a is a BET nitrogen adsorption isotherm of mesoporous and acidicactivated carbon particles CA-10, and mesoporous, basic, andreduced-oxygen activated carbon particles TA4-CA-10.

FIG. 1 b is a BET nitrogen adsorption isotherm of mesoporous and basicactivated carbon particles RGC, and mesoporous, basic, andreduced-oxygen activated carbon THe4-RGC.

FIG. 2 a is a mesopore volume distribution of the particles of FIG. 1 a.

FIG. 2 b is a mesopore volume distribution of the particles of FIG. 1 b.

FIG. 3 a is a point-of-zero-charge graph of the particles of FIG. 1 a.

FIG. 3 b is a point-of-zero-charge graph of the particles of FIG. 1 b.

FIG. 4 is a cross sectional side view of an axial flow filter made inaccordance with the present invention.

FIG. 5 a illustrates the E. coli bath concentration as a function oftime for the activated carbon particles of FIG. 1 a.

FIG. 5 b illustrates the E. coli bath concentration as a function oftime for activated carbon particles of FIG. 1 b.

FIG. 6 a illustrates the MS-2 bath concentration as a function of timefor the activated carbon particles of FIG. 1 a.

FIG. 6 b illustrates the MS-2 bath concentration as a function of timefor the activated carbon particles of FIG. 1 b.

FIG. 7 a illustrates the E. coli flow concentration as a function of thecumulative volume of water through 2 filters; one containing RGCmesoporous and basic activated carbon, and the other containing coconutmicroporous activated carbon particles.

FIG. 7 b illustrates the MS-2 flow concentration as a function of thecumulative volume of water through of 2 filters; one containing RGCmesoporous and basic activated carbon, and the other containing coconutmicroporous activated carbon particles.

DETAILED DESCRIPTION

All documents cited are, in relevant part, incorporated herein byreference. The citation of any document is not to be construed as anadmission that it is prior art with respect to the present invention.

I. Definitions

As used herein, the terms “filters” and “filtration” refer to structuresand mechanisms, respectively, associated with microorganism removal(and/or other contaminant removal), via primarily adsorption and/or sizeexclusion to a lesser extent.

As used herein, the phrase “filter material” is intended to refer to anaggregate of filter particles. The aggregate of the filter particlesforming a filter material can be either homogeneous or heterogeneous.The filter particles can be uniformly or non-uniformly distributed(e.g., layers of different filter particles) within the filter material.The filter particles forming a filter material also need not beidentical in shape or size and may be provided in either a loose orinterconnected form. For example, a filter material might comprisemesoporous and basic activated carbon particles in combination withactivated carbon fibers, and these filter particles may be eitherprovided in loose association or partially or wholly bonded by apolymeric binder or other means to form an integral structure.

As used herein, the phrase “filter particle” is intended to refer to anindividual member or piece, which is used to form at least part of afilter material. For example, a fiber, a granule, a bead, etc. are eachconsidered filter particles herein. Further, the filter particles canvary in size, from impalpable filter particles (e.g., a very finepowder) to palpable filter particles.

As used herein, the phrase “filter material pore volume” refers to thetotal volume of the inter-particle pores in the filter material withsizes larger than 0.1 μm.

As used herein, the phrase “filter material total volume” refers to thesum of the inter-particle pore volume and the volume occupied by thefilter particles.

As used herein, the terms “microorganism”, “microbiological organism”and “pathogen” are used interchangeably. These terms refer to varioustypes of microorganisms that can be characterized as bacteria, viruses,parasites, protozoa, and germs.

As used herein, the phrase “Bacteria Removal Index” (BRI) of filterparticles is defined as:

BRI=100×[1−(bath concentration of E. coli bacteria atequilibrium/control concentration of E. coli bacteria)],

wherein “bath concentration of E. coli bacteria at equilibrium” refersto the concentration of bacteria at equilibrium in a bath that containsa mass of filter particles having a total external surface area of 1400cm² and Sauter mean diameter less than 55 μm, as discussed more fullyhereafter. Equilibrium is reached when the E. coli concentration, asmeasured at two time points 2 hours apart, remains unchanged to withinhalf order of magnitude. The phrase “control concentration of E. colibacteria” refers to the concentration of E. coli bacteria in the controlbath, and is equal to about 3.7×10⁹ CFU/L. The Sauter mean diameter isthe diameter of a particle whose surface-to-volume ratio is equal tothat of the entire particle distribution. Note that the term “CFU/L”denotes “colony-forming units per liter”, which is a typical term usedin E. coli counting. The BRI index is measured without application ofchemical agents that provide bactericidal effects. An equivalent way toreport the removal capability of filter particles is with the “BacteriaLog Removal Index” (BLRI), which is defined as:

BLRI=−log [1−(BRI/100)].

The BLRI has units of “log” (where “log” stands for logarithm). Forexample, filter particles that have a BRI equal to 99.99% have a BLRIequal to 4 log. A test procedure for determining BRI and BLRI values isprovided hereafter.

As used herein, the phrase “Virus Removal Index” (VRI) for filterparticles is defined as:

VRI=100×[1−(bath concentration of MS-2 phages at equilibrium/controlconcentration of MS-2 phages)],

wherein “bath concentration of MS-2 phages at equilibrium” refers to theconcentration of phages at equilibrium in a bath that contains a mass offilter particles having a total external surface area of 1400 cm² andSauter mean diameter less than 55 μm, as discussed more fully hereafter.Equilibrium is reached when the MS-2 concentration, as measured at twotime points 2 hours apart, remains unchanged to within half order ofmagnitude. The phrase “control concentration of MS-2 phages” refers tothe concentration of MS-2 phages in the control bath, and is equal toabout 6.7×10⁷ PFU/L. Note that the term “PFU/L” denotes “plaque-formingunits per liter”, which is a typical term used in MS-2 counting. The VRIindex is measured without application of chemical agents that providevirucidal effects. An equivalent way to report the removal capability offilter particles is with the “Viruses Log Removal Index” (VLRI), whichis defined as:

VLRI=−log [1−(VRI/100)].

The VLRI has units of “log” (where “log” is the logarithm). For example,filter particles that have a VRI equal to 99.9% have a VLRI equal to 3log. A test procedure for determining VRI and VLRI values is providedhereafter.

As used herein, the phrase “Filter Bacteria Log Removal (F-BLR)” refersto the bacteria removal capability of the filter after the flow of thefirst 2,000 filter material pore volumes. The F-BLR is defined andcalculated as:

F-BLR=−log [(effluent concentration of E. coli)/(influent concentrationof E. coli)],

where the “influent concentration of E. coli” is set to about 1×10⁸CFU/L continuously throughout the test and the “effluent concentrationof E. coli” is measured after about 2,000 filter material pore volumesflow through the filter. F-BLR has units of “log” (where “log” is thelogarithm). Note that if the effluent concentration is below the limitof detection of the technique used to assay, then the effluentconcentration for the calculation of the F-BLR is considered to be thelimit of detection. Also, note that the F-BLR is measured withoutapplication of chemical agents that provide bactericidal effects.

As used herein, the phrase “Filter Viruses Log Removal (F-VLR)” refersto the virus removal capability of the filter after the flow of thefirst 2,000 filter material pore volumes. The F-VLR is defined andcalculated as:

F-VLR=−log [(effluent concentration of MS-2)/(influent concentration ofMS-2)],

where the “influent concentration of MS-2” is set to about 1×10⁷ PFU/Lcontinuously throughout the test and the “effluent concentration ofMS-2” is measured after about 2,000 filter material pore volumes flowthrough the filter. F-VLR has units of “log” (where “log” is thelogarithm). Note that if the effluent concentration is below the limitof detection of the technique used to assay, then the effluentconcentration for the calculation of the F-VLR is considered to be thelimit of detection. Also, note that the F-VLR is measured withoutapplication of chemical agents that provide virucidal effects.

As used herein, the phrase “total external surface area” is intended torefer to the total geometric external surface area of one or more of thefilter particles, as discussed more fully hereafter.

As used herein, the phrase “specific external surface area” is intendedto refer to the total external surface area per unit mass of the filterparticles, as discussed more fully hereafter.

As used herein, the term “micropore” is intended to refer to anintra-particle pore having a width or diameter less than 2 nm (orequivalently, 20 Å).

As used herein, the term “mesopore” is intended to refer to anintra-particle pore having a width or diameter between 2 nm and 50 nm(or equivalently, between 20 Å and 500 Å).

As used herein, the term “macropore” is intended to refer to anintra-particle pore having a width or diameter greater than 50 nm (orequivalently, 500 Å).

As used herein, the phrase “total pore volume” and its derivatives areintended to refer to the volume of all the intra-particle pores, i.e.,micropores, mesopores, and macropores. The total pore volume iscalculated as the volume of nitrogen adsorbed at a relative pressure of0.9814 using the BET process (ASTM D 4820-99 standard), a process wellknown in the art.

As used herein, the phrase “micropore volume” and its derivatives areintended to refer to the volume of all micropores. The micropore volumeis calculated from the volume of nitrogen adsorbed at a relativepressure of 0.15 using the BET process (ASTM D 4820-99 standard), aprocess well known in the art.

As used herein, the phrase “sum of the mesopore and macropore volumes”and its derivatives are intended to refer to the volume of all mesoporesand macropores. The sum of the mesopore and macropore volumes is equalto the difference between the total pore volume and micropore volume, orequivalently, is calculated from the difference between the volumes ofnitrogen adsorbed at relative pressures of 0.9814 and 0.15 using the BETprocess (ASTM D 4820-99 standard), a process well known in the art.

As used herein, the phrase “pore size distribution in the mesoporerange” is intended to refer to the distribution of the pore size ascalculated by the Barrett, Joyner, and Halenda (BJH) process, a processwell known in the art.

As used herein, the term “carbonization” and its derivatives areintended to refer to a process in which the non-carbon atoms in acarbonaceous substance are reduced.

As used herein, the term “activation” and its derivatives are intendedto refer to a process in which a carbonized substance is rendered moreporous.

As used herein, the term “activated carbon particles” or “activatedcarbon filter particles” and their derivatives are intended to refer tocarbon particles that have been subjected to an activation process.

As used herein, the phrase “point of zero charge” is intended to referto the pH above which the total surface of the carbon particles isnegatively charged. A well known test procedure for determining thepoint of zero charge is set forth hereafter.

As used herein, the term “basic” is intended to refer to filterparticles with a point of zero charge greater than 7.

As used herein, the term “acidic” is intended to refer to filterparticles with a point of zero charge less than 7.

As used herein, the phrase “mesoporous activated carbon filter particle”refers to an activated carbon filter particle wherein the sum of themesopore and macropore volumes may be greater than 0.12 mL/g.

As used herein, the phrase “microporous activated carbon filterparticle” refers to an activated carbon filter particle wherein the sumof the mesopore and macropore volumes may be less than 0.12 mL/g.

As used herein, the phrase “mesoporous and basic activated carbon filterparticle” is intended to refer to an activated carbon filter particlewherein the sum of the mesopore and macropore volumes may be greaterthan 0.12 mL/g and has a point of zero charge greater than 7.

As used herein, the phrase “mesoporous, basic, and reduced-oxygenactivated carbon filter particle” is intended to refer to an activatedcarbon filter particle wherein the sum of the mesopore and macroporevolumes may be greater than 0.12 mL/g, has a point of zero chargegreater than 7, and has a bulk oxygen percentage by weight of 1.5% orless.

As used herein, the phrase “mesoporous and acidic activated carbonfilter particle” is intended to refer to an activated carbon filterparticle wherein the sum of the mesopore and macropore volumes may begreater than 0.12 mL/g and has a point of zero charge less than 7.

As used herein, the phrase “starting material” refers to any precursorcontaining mesopores and macropores or capable of yielding mesopores andmacropores during carbonization and/or activation.

As used herein, the phrase “axial flow” refers to flow through a planarsurface and perpendicularly to that surface.

As used herein, the phrase “radial flow” typically refers to flowthrough essentially cylindrical or essentially conical surfaces andperpendicularly to those surfaces.

As used herein, the phrase “face area” refers to the area of the filtermaterial initially exposed to the influent water. For example, in thecase of axial flow filters, the face area is the cross sectional area ofthe filter material at the entrance of the fluid, and in the case of theradial flow filter, the face area is the outside area of the filtermaterial.

As used herein, the phrase “filter depth” refers to the linear distancethat the influent water travels from the entrance to the exit of thefilter material. For example, in the case of axial flow filters, thefilter depth is the thickness of the filter material, and in the case ofthe radial flow filter, the filter depth is half of the differencebetween the outside and inside diameters of the filter material.

As used herein, the phrases “average fluid residence time” and/or“average fluid contact time” refer to the average time that the fluid isin contact with the filter particles inside the filter as it travelsthrough the filter material, and are calculated as the ratio of thefilter material pore volume to the fluid flow rate.

As used herein, the phrases “filter porosity” and/or “filter bedporosity” refer to the ratio of the filter material pore volume to thefilter material total volume.

As used herein, the phrase “inlet” refers to the means in which a fluidis able to enter the filter or filter material. For example, the inletcan be a structure that is part of the filter, or the filter materialface area.

As used herein, an “outlet” refers to the means in which a fluid is ableto exit the filter or filter material. For example, the outlet can be astructure that is part of the filter, or the cross sectional area of thefilter material at the exit of the fluid.

II. Mesoporous Activated Carbon Filter Particles

Unexpectedly it has been found that mesoporous activated carbon filterparticles adsorb a larger number of microorganisms compared tomicroporous activated carbon filter particles. Also, unexpectedly it hasbeen found that mesoporous and basic activated carbon filter particlesadsorb a larger number of microorganisms compared to that adsorbed bymesoporous and acidic activated carbon filter particles. Furthermore, ithas been found unexpectedly that mesoporous, basic, and reduced-oxygenactivated carbon filter particles adsorb a larger number ofmicroorganisms compared to that adsorbed by mesoporous and basicactivated carbon filter particles without reduced bulk oxygen percentageby weight.

Although not wishing to be bound by any theory, applicants hypothesizethat, with regard to porosity, a large number of mesopores and/ormacropores provide more convenient adsorption sites (openings orentrances of the mesopores/macropores) for the pathogens, theirfimbriae, and surface polymers (e.g. proteins, lipopolysaccharides,oligosaccharides and polysaccharides) that constitute the outermembranes, capsids and envelopes of the pathogens because the typicalsize of such is similar to that of the entrances of the mesopores andmacropores. Also, mesoporosity and macroporosity may correlate with oneor more surface properties of the carbon, such as surface roughness.

Also, not wishing to be bound by theory, applicants hypothesize thatbasic activated carbon surfaces may contain the types of functionalitythat are necessary to attract a larger number of microorganisms comparedto those attracted by an acidic carbon surface. This enhanced adsorptiononto the basic carbon surfaces might be attributed to the fact that thebasic carbon surfaces attract the typically negatively-chargedmicroorganisms and functional groups on their surface. Applicantsfurther hypothesize that basic carbon is capable of producingdisinfectants when placed in water by reducing molecular oxygen.Although the final product of the reduction is hydroxide, applicantsbelieve that reactive oxygen intermediates, such as superoxide,hydroperoxide, and/or hydroxy radicals, are formed and maybesufficiently long-lived to diffuse from carbon into bulk solution.

Furthermore, applicants believe that carbon may become more basic as thebulk oxygen percentage by weight is reduced. A low bulk oxygenpercentage by weight may lead to improved bacteria/viruses adsorptionbecause there will be: (1) less carboxylic acids and hence a lessnegative surface to repel bacteria/viruses; and (2) a less hydratedsurface so that water is more easily displaced by bacteria/viruses asthey attempt to adsorb to the surface (i.e., less of an energy penaltyfor the bacteria/virus to displace other species already occupying siteson the surface). This latter reason (i.e., a less hydrated surface) alsoties in with the idea that in some embodiments, the surface, discussedhereafter, may be somewhat hydrophobic (that is, it may have just enoughoxygen substitution on the edge carbon atoms to allow it to wet out, butnot so much as to make it excessively hydrophilic).

The filter particles can be provided in a variety of shapes and sizes.For example, the filter particles can be provided in simple forms suchas powder, granules, fibers, and beads. The filter particles can beprovided in the shape of a sphere, polyhedron, cylinder, as well asother symmetrical, asymmetrical, and irregular shapes. Further, thefilter particles can also be formed into complex forms such as webs,screens, meshes, non-wovens, wovens, and bonded blocks, which may or maynot be formed from the simple forms described above. Like shape, thesize of the filter particle can also vary, and the size need not beuniform among filter particles used in any single filter. In fact, itcan be desirable to provide filter particles having different sizes in asingle filter. Generally, the size of the filter particles may bebetween about 0.1 μm and about 10 mm, in some embodiments between about0.2 μm and about 5 mm, in some embodiments between about 0.4 μm andabout 1 mm, and in some embodiments between about 1 μm and about 500 μm.For spherical and cylindrical particles (e.g., fibers, beads, etc.), theabove-described dimensions refer to the diameter of the filterparticles. For filter particles having substantially different shapes,the above-described dimensions refer to the largest dimension (e.g.length, width, or height).

The filter particles may be the product of any precursor that containsmesopores and macropores or generates mesopores and macropores duringcarbonization and/or activation. For example, and not by way oflimitation, the filter particles can be wood-based activated carbonparticles, coal-based activated carbon particles, peat-based activatedcarbon particles, pitch-based activated carbon particles, tar-basedactivated carbon particles, bean-based activated carbon particles, otherlignocellulosic-based activated carbon particles, and mixtures thereof.

Activated carbon can display acidic, neutral, or basic properties. Theacidic properties may be associated with oxygen-containingfunctionalities or functional groups, such as, and not by way oflimitation, phenols, carboxyls, lactones, hydroquinones, anhydrides, andketones. The basic properties may be associated with functionalitiessuch as pyrones, chromenes, ethers, carbonyls, as well as the basalplane π electrons. The acidity or basicity of the activated carbonparticles is determined with the “point of zero charge” technique(Newcombe, G., et al., Colloids and Surfaces A: Physicochemical andEngineering Aspects, 78, 65-71 (1993)), the substance of which isincorporated herein by reference. The technique is further described insection VI hereafter. Examples of filter particles may have a point ofzero charge between 1 and 14, in some embodiments greater than about 4,in other embodiments greater than about 6, in other embodiments greaterthan about 7, in other embodiments greater than about 8, in otherembodiments greater than about 9, and in yet other embodiments betweenabout 9 and about 12.

The point of zero charge of activated carbons inversely correlates withtheir bulk oxygen percentage by weight. Examples of filter particles mayhave a bulk oxygen percentage by weight less than about 5%, in someembodiments less than about 2.5%, in some embodiments less than about2.3%, in some embodiments less than about 2%, in some embodiments lessthan about 1.2%, and in some embodiments less than about 1%, and/orgreater than about 0.1%, in some embodiments greater than about 0.2%, insome embodiments greater than about 0.25%, and in some embodimentsgreater than about 0.3%. Also, the point of zero charge of activatedcarbon particles correlates with the ORP of the water containing theparticles because the point of zero charge is a measure of the abilityof the carbon to reduce oxygen (at least for basic carbons). Examples offilter particles may have an ORP less than about 570 mV, in someembodiments less than about 465 mV, in some embodiments less than about400, in some embodiments less than about 360 mV, in some embodimentsless than about 325 mV, and in some embodiments between about 290 mV andabout 175 mV.

The electric resistance of the activated carbon filter particles orfilter material relates to their ability to form a filter block. Forexample, a resistive heating method can be used to form filter blocks,wherein a filter material is heated by passing electricity between 2ends of the filter material. The electric resistance of the filtermaterial will control its ability to heat in a short time. The electricresistance is measured by forming filter blocks using conditions asthose mentioned in Examples 3 and 4, and measuring the electricresistance between the 2 faces of the block by contacting them with 2electrodes from a voltmeter. Exemplary electric resistances of thefilters of Examples 3 and 4 are about 350Ω and about 40Ω, respectively.Also, the respective electric resistances of filters made with CARBOCHEMCA-10 of Example 1, and TA4-CA10 of Example 2, are about 1.3 MΩ, andabout 100Ω.

Filter particles may be achieved by way of treating a starting materialas described herein. The treatment conditions may include atmospherecomposition, pressure, temperature, and/or time. The atmospheres of thepresent invention may be reducing or inert. Heating the filter particlesin the presence of reducing atmospheres, steam, or inert atmospheresyields filter material with reduced surface oxygen functionality.Examples of suitable reducing atmospheres may include hydrogen,nitrogen, dissociated ammonia, carbon monoxide, and/or mixtures.Examples of suitable inert atmospheres may include argon, helium, and/ormixtures thereof.

The treatment temperature, when the activated carbon particles do notcontain any noble metal catalysts (e.g., platinum, gold, palladium) maybe between about 600° C. and about 1,200° C., in some embodimentsbetween about 700° C. and about 1,100° C., in some embodiments betweenabout 800° C. and about 1,050° C., and in some embodiments between about900° C. and about 1,000° C. If the activated carbon particles containnoble metal catalysts, the treatment temperature may be between about100° C. and about 800° C., in some embodiments between about 200° C. andabout 700° C., in some embodiments between about 300° C. and about 600°C., and in some embodiments between about 350° C. and about 550° C.

The treatment time may be between about 2 minutes and about 10 hours, insome embodiments between about 5 minutes and about 8 hours, in someembodiments between about 10 minutes and about 7 hours, and in someembodiments between about 20 minutes and about 6 hours. The gas flowrate may be between about 0.25 standard L/h.g (i.e., standard liters perhour and gram of carbon; 0.009 standard ft³/h.g) and about 60 standardL/h.g (2.1 standard ft³/h.g), in some embodiments between about 0.5standard L/h.g (0.018 standard ft³/h.g) and about 30 standard L/h.g(1.06 standard ft³/h.g), in some embodiments between about 1.0 standardL/h.g (0.035 standard ft³/h.g) and about 20 standard L/h.g (0.7 standardft³/h.g), and in some embodiments between about 5 standard L/h.g (0.18standard ft³/h.g) and about 10 standard L/h.g (0.35 standard ft³/h.g).The pressure can be maintained greater than, equal to, or less thanatmospheric during the treatment time. As will be appreciated, otherprocesses for producing a mesoporous, basic, and reduced-oxygenactivated carbon filter material can be employed. Also, such treatmentof a starting material as described above may be repeated multipletimes, depending on the starting material, in order to obtain a filtermaterial.

A starting material may be commercially obtained, or may be made by themethods which are well known in the art, as described in, for example,Jagtoyen, M., and F. Derbyshire, Carbon, 36(7-8), 1085-1097 (1998), andEvans, et al., Carbon, 37, 269-274 (1999), and Ryoo et al., J. Phys.Chem. B, 103(37), 7743-7746 (1999), the substances of which are hereinincorporated by reference. Typical chemicals used foractivation/carbonization include phosphoric acid, zinc chloride,ammonium phosphate, etc., which may be used in combination with themethods described in the two immediately cited journals.

The Brunauer, Emmett and Teller (BET) specific surface area and theBarrett, Joyner, and Halenda (BJH) pore size distribution can be used tocharacterize the pore structure of particles. In some embodiments, theBET specific surface area of the filter particles may be between about500 m²/g and about 3,000 m²/g, in some embodiments between about 600m²/g to about 2,800 m²/g, in some embodiments between about 800 m²/g andabout 2,500 m²/g, and in some embodiments between about 1,000 m²/g andabout 2,000 m²/g. Referring to FIG. 1 a, examples of nitrogen adsorptionisotherms, using the BET process, of a mesoporous, basic, andreduced-oxygen wood-based activated carbon (TA4-CA-10), and a mesoporousand acidic wood-based activated carbon (CA-10) are illustrated.Referring to FIG. 1 b, examples of nitrogen adsorption isotherms, usingthe BET process, of a mesoporous and basic wood-based activated carbon(RGC), and a mesoporous, basic, and reduced-oxygen wood-based activatedcarbon (THe4-RGC) are illustrated.

The total pore volume of the mesoporous and basic activated carbonparticles is measured during the BET nitrogen adsorption and iscalculated as the volume of nitrogen adsorbed at a relative pressure,P/P₀, of 0.9814. More specifically and as is well known in the art, thetotal pore volume is calculated by multiplying the “volume of nitrogenadsorbed in mL(STP)/g” at a relative pressure of 0.9814 with theconversion factor 0.00156, that converts the volume of nitrogen at STP(standard temperature and pressure) to liquid. The total pore volume ofembodiments of the filter particles may be greater than about 0.4 mL/g,or greater than about 0.7 mL/g, or greater than about 1.3 mL/g, orgreater than about 2 mL/g, and/or less than about 3 mL/g, or less thanabout 2.6 mL/g, or less than about 2 mL/g, or less than about 1.5 mL/g.

The sum of the mesopore and macropore volumes is measured during the BETnitrogen adsorption and calculated as the difference between the totalpore volume and the volume of nitrogen adsorbed at P/P₀ of 0.15. The sumof the mesopore and macropore volumes of embodiments of the filterparticles may be greater than about 0.12 mL/g, or greater than about 0.2mL/g, or greater than about 0.4 mL/g, or greater than about 0.6 mL/g, orgreater than about 0.75 mL/g, and/or less than about 2.2 mL/g, or lessthan about 2 mL/g, or less than about 1.5 mL/g, or less than about 1.2mL/g, or less than about 1 mL/g.

The BJH pore size distribution can be measured using the Barrett,Joyner, and Halenda (BJH) process, which is described in J. Amer. Chem.Soc., 73, 373-80 (1951) and Gregg and Sing, ADSORPTION, SURFACE AREA,AND POROSITY, 2nd edition, Academic Press, New York (1982), thesubstances of which are incorporated herein by reference. In oneembodiment, the pore volume may be at least about 0.01 mL/g for any porediameter between about 4 nm and about 6 nm. In another embodiment, thepore volume may be between about 0.01 mL/g and about 0.04 mL/g for anypore diameter between about 4 nm and about 6 nm. In yet anotherembodiment, the pore volume may be at least about 0.03 mL/g for porediameters between about 4 nm and about 6 nm or is between about 0.03mL/g and about 0.06 mL/g. In yet another embodiment, the pore volume maybe between about 0.015 mL/g and about 0.06 mL/g for pore diametersbetween about 4 nm and about 6 nm. FIG. 2 a illustrates examples ofmesopore volume distributions, as calculated by the BJH process, of amesoporous, basic, and reduced-oxygen activated carbon (TA4-CA-10), anda mesoporous and acidic wood-based activated carbon (CA-10). FIG. 2 billustrates examples of mesopore volume distributions, as calculated bythe BJH process, of a mesoporous and basic wood-based activated carbon(RGC), and a mesoporous, basic, and reduced-oxygen wood-based activatedcarbon (THe4-RGC).

The ratio of the sum of the mesopore and macropore volumes to the totalpore volume may be greater than about 0.3, in some embodiments greaterthan about 0.4, in some embodiments greater than about 0.6, and in someembodiments between about 0.7 and about 1.

The total external surface area is calculated by multiplying thespecific external surface area by the mass of the filter particles, andis based on the dimensions of the filter particles. For example, thespecific external surface area of mono-dispersed (i.e., with uniformdiameter) fibers is calculated as the ratio of the area of the fibers(neglecting the 2 cross sectional areas at the ends of the fibers) tothe weight of the fibers. Thus, the specific external surface area ofthe fibers is equal to: 4/Dρ, where D is the fiber diameter and ρ is thefiber density. For monodispersed spherical particles, similarcalculations yield the specific external surface area as equal to: 6/Dρ,where D is the particle diameter and ρ is the particle density. Forpoly-dispersed fibers, spherical or irregular particles, the specificexternal surface area is calculated using the same respective formulaeas above after substituting D _(3,2) for D, where D _(3,2) is the Sautermean diameter, which is the diameter of a particle whosesurface-to-volume ratio is equal to that of the entire particledistribution. A process, well known in the art, to measure the Sautermean diameter is by laser diffraction, for example using the Malvernequipment (Malvern Instruments Ltd., Malvern, U.K.). The specificexternal surface area of the filter particles may be between about 10cm²/g and about 100,000 cm²/g, in some embodiments between about 50cm²/g and about 50,000 cm²/g, in some embodiments between about 100cm²/g and about 10,000 cm²/g, and in some embodiments between about 500cm²/g and about 7,000 cm²/g.

The BRI of the mesoporous, or mesoporous and basic, or mesoporous, basicand reduced-oxygen activated carbon particles, when measured accordingto the test procedure set forth herein, may be greater than about 99%,in some embodiments greater than about 99.9%, in some embodimentsgreater than about 99.99%, and in some embodiments greater than about99.999%. Equivalently, the BLRI of the mesoporous, or mesoporous andbasic, or mesoporous, basic and reduced-oxygen activated carbonparticles may be greater than about 2 log, in some embodiments greaterthan about 3 log, in some embodiments greater than about 4 log, and insome embodiments greater than about 5 log. The VRI of the mesoporous, ormesoporous and basic, or mesoporous, basic and reduced-oxygen activatedcarbon particles, when measured according to the test procedure setforth herein, may be greater than about 90%, in some embodiments greaterthan about 95%, in some embodiments greater than about 99%, and in someembodiments greater than about 99.9%. Equivalently, the VLRI of themesoporous, or mesoporous and basic, or mesoporous, basic andreduced-oxygen activated carbon particles may be greater than about 1log, in some embodiments greater than about 1.3 log, in some embodimentsgreater than about 2 log, and in some embodiments greater than about 3log.

The steady state, one-dimensional, “clean” bed filtration theory(assuming negligible dispersive transport and desorption ofmicroorganisms) for an axial flow filter (Yao et al., Environ. Sci.Technol. 5, 1102-1112 (1971)), the substance of which is incorporatedherein by reference, describes that:

C/C ₀=exp(−λL),  (1)

where C is the effluent concentration, C₀ is the influent concentration,λ is the filter coefficient with units of reciprocal length, and L isthe depth of the filter. Note that based on the definitions above, thenumber of collisions that a non-attaching microorganism will experienceas it travels over a distance L through the filter will be (λ/α)L, wherea is the “clean” bed sticking coefficient (also called, collisionefficiency), defined as the ratio of the number of microorganisms thatstick to the collector surface to the number of microorganisms thatstrike the collector surface. Equation 1 is also valid for radial flowfilters if L is substituted by R₀−R_(i), where R₀ is the outside radiusand R_(i) is the inside radius, and the filter coefficient is averagedover the thickness of the filter. The filter coefficient for aparticle-containing bed (not fibers) is as follows:

λ=(3(1−ε)ηα)/2d _(c),  (2)

where ε is the filter bed porosity, η is the single-collectorefficiency, defined as the ratio of the number of microorganisms thatstrike the collector surface to the number of microorganisms that flowtowards the collector surface, and d_(c) is the collector particlediameter. The factor (3/2) in the formula above is valid for sphericalor spherical-like particles. For cylindrical particles (e.g. fibers) theterm becomes (4/π), and d_(c) is then the diameter of the cylinder.Also, note that the term “clean” bed means that the collector surfaceshave not yet accumulated enough microorganisms to cause a reduction inthe deposition efficiency of the new microorganisms (i.e., blocking).

Based on the above “clean” bed filtration model, the F-BLR and F-VLR canbe calculated as follows:

F-BLR or F-VLR=−log(C/C ₀)=(λL/2.3).  (3)

The single-collector efficiency, η, is calculated using the Rajagopalanand Tien model (RT model; AIChE J., 22(3), 523-533 (1976), and AIChE J.,28, 871-872 (1982)) as follows:

η=4A _(S) ^(1/3) Pe ^(−2/3) +A _(S) Lo ^(1/8) R ^(15/8)+0.00338A _(S) G^(6/5) R ^(−2/5),  (4)

where

${A_{S} = \frac{2\left( {1 - \gamma^{5}} \right)}{2 - {3\gamma} + {3\gamma^{5}} - {2\gamma^{6}}}},$

γ=(1−ε)^(1/3), Pe is the dimensionless Peclet number

${{Pe} = \frac{3\mspace{11mu} {\mu\pi}\; U\; d_{c}d_{m}}{kT}},$

Lo is the dimensionless London-van der Waals number

${{Lo} = \frac{4\; H}{9\mspace{11mu} {\pi\mu}\; d_{m}^{2}U}},$

R is the dimensionless interception number

${R = \frac{d_{m}}{d_{c}}},$

G is the dimensionless sedimentation number

${G = \frac{{g\left( {\rho_{m} - \rho_{f}} \right)}d_{m}^{2}}{18\mspace{11mu} \mu \; U}},$

μ is the dynamic fluid viscosity (equal to 1 mPa·s for water), U is thesuperficial fluid velocity (calculated as: U=4Q/πD², for axial flowfilters, where Q is the fluid flowrate, and D is the diameter of theface area of the filter; and U(R)=Q/2πRX for radial flow filters, whereX is the length of the filter, and R is the radial position betweenR_(i) and R₀), d_(m) is the microorganism diameter (or diameter of anequivalent sphere, if the microorganism is non spherical), k is theBoltzmann's constant (equal to 1.38×10⁻²³ kg·m²/s²·K), T is the fluidtemperature, H is the Hamaker constant (it is typically equal to 10⁻²⁰J), g is the gravitational constant (equal to 9.81 m/s²), ρ_(m) is thedensity of the microorganisms, and ρ_(f) is the fluid density (equal to1 g/mL for water). For the purposes and the materials of the presentinvention, H is equal to 10⁻²⁰ J, T is equal to 298 K, ρ_(m) is equal to1.05 g/mL, μ is equal to 1 mPa·s. Also, for the purposes of the presentinvention, d_(c) is the volume median diameter D_(V,0.5), which is theparticle diameter such that 50% of the total particle volume is inparticles of smaller diameter. Also, the average fluid residence time iscalculated as:

$\begin{matrix}{{{\tau = \frac{{ɛ\pi}\; D^{2}L}{4Q}},{{for}\mspace{14mu} {axial}\mspace{14mu} {flow}\mspace{14mu} {filters}},{and}}{{\tau = \frac{{{ɛ\pi}\left( {R_{0}^{2} - R_{i}^{2}} \right)}X}{Q}},{{for}\mspace{14mu} {radial}\mspace{14mu} {flow}\mspace{14mu} {{filters}.}}}} & (5)\end{matrix}$

The sticking coefficient, α, is typically calculated experimentally, forexample using the “microbe and radiolabel kinesis” (MARK) techniquedescribed in Gross et al. (Water Res., 29(4), 1151-1158 (1995)). Thesingle-collector efficiency, η, of examples of the filters describedherein may be greater than about 0.002, in some embodiments greater thanabout 0.02, in some embodiments greater than about 0.2, in someembodiments greater than about 0.4, in some embodiments greater thanabout 0.6, and in some embodiments between about 0.8 and about 1. Thefilter coefficient, λ, of examples of the filters described herein maybe greater than about 10 m⁻¹, in some embodiments greater than about 20m⁻¹, in some embodiments greater than about 30 m⁻¹, in some embodimentsgreater than about 40 m⁻¹, and/or less than about 20,000 m⁻¹, in someembodiments less than about 10,000 m⁻¹, in some embodiments less thanabout 5,000 m⁻¹, and in some embodiments less than about 1,000 m⁻¹.

The F-BLR of filters containing mesoporous, or mesoporous and basic, ormesoporous, basic, and reduced-oxygen activated carbon particles, whenmeasured according to the test procedure set forth herein, may begreater than about 2 logs, in some embodiments greater than about 3logs, in some embodiments greater than about 4 logs, and in someembodiments greater than about 6 logs. The F-VLR of filters containingmesoporous, or mesoporous and basic, or mesoporous, basic, andreduced-oxygen activated carbon particles, when measured according tothe test procedure set forth herein, may be greater than about 1 log, insome embodiments greater than about 2 logs, in some embodiments greaterthan about 3 logs, and in some embodiments greater than about 4 logs.

In one embodiment of the present invention, the filter particlescomprise mesoporous activated carbon particles that are wood-basedactivated carbon particles. These particles have a BET specific surfacearea between about 1,000 m²/g and about 2,000 m²/g, total pore volumebetween about 0.8 mL/g and about 2 mL/g, and sum of the mesopore andmacropore volumes between about 0.4 mL/g and about 1.5 mL/g.

In another embodiment of the present invention, the filter particlescomprise mesoporous and basic activated carbon particles that arewood-based activated carbon particles. These particles have a BETspecific surface area between about 1,000 m²/g and about 2,000 m²/g,total pore volume between about 0.8 mL/g and about 2 mL/g, and sum ofthe mesopore and macropore volumes between about 0.4 mL/g and about 1.5mL/g.

In yet another embodiment of the present invention, the filter particlescomprise mesoporous, basic, and reduced-oxygen activated carbonparticles that were initially acidic and rendered basic andreduced-oxygen with treatment in a dissociated ammonia atmosphere. Theseparticles are wood-based activated carbon particles. The treatmenttemperature is between about 925° C. and about 1,000° C., the ammoniaflow rate is between about 1 standard L/h.g and about 20 standard L/h.g,and the treatment time is between about 10 minutes and about 7 hours.These particles have a BET specific surface area between about 800 m²/gand about 2,500 m²/g, total pore volume between about 0.7 mL/g and about2.5 mL/g, and sum of the mesopore and macropore volumes between about0.21 mL/g and about 1.7 mL/g. A non-limiting example of an acidicactivated carbon that is converted to a basic and reduced-oxygenactivated carbon is set forth below.

In even yet another embodiment of the present invention, the filterparticles comprise mesoporous, basic, and reduced-oxygen activatedcarbon particles, that were initially mesoporous and basic, withtreatment in an inert (i.e., helium) atmosphere. These particles arewood-based activated carbon particles. The treatment temperature isbetween about 800° C. and about 1,000° C., the helium flowrate isbetween about 1 standard L/h.g and about 20 standard L/h.g, and thetreatment time is between about 10 minutes and about 7 hours. Theseparticles have a BET specific surface area between about 800 m²/g andabout 2,500 m²/g, total pore volume between about 0.7 mL/g and about 2.5mL/g, and sum of the mesopore and macropore volumes between about 0.21mL/g and about 1.7 mL/g. A non-limiting example of a basic activatedcarbon that is converted to a basic and reduced-oxygen activated carbonis set forth below.

III. Treatment Examples Example 1 Treatment of a Mesoporous and AcidicActivated Carbon to Produce a Mesoporous, Basic, and Reduced-OxygenActivated Carbon

About 2 kg of the CARBOCHEM® CA-10 mesoporous and acidic wood-basedactivated carbon particles from Carbochem, Inc., of Ardmore, Pa., areplaced on the belt of a furnace Model BAC-M manufactured by C. I. Hayes,Inc., of Cranston, R.I. The furnace temperature is set to about 950° C.,the treatment time is about 4 hours, and the atmosphere is dissociatedammonia flowing with a volumetric flow rate of about 12,800 standard L/h(i.e., about 450 standard ft³/h, or equivalently, about 6.4 standardL/h.g). The treated activated carbon particles are called TA4-CA-10, andtheir BET isotherm, mesopore volume distribution, and point of zerocharge analyses are illustrated in FIGS. 1 a, 2 a, and 3 a,respectively. Numerical values for BET, the sum of mesopore andmacropore volumes, point of zero charge, BRI/BLRI, VRI/VLRI, bulk oxygenpercentage by weight, and ORP are shown in Section VI.

Example 2

Treatment of a Mesoporous and Basic Activated Carbon to Produce aMesoporous, Basic, and Reduced-Oxygen Activated Carbon

About 2 kg of the MeadWestvaco Nuchar® RGC mesoporous and basicwood-based activated carbon particles from MeadWestvaco Corp., ofCovington, Va., are placed on the belt of a furnace Model BAC-Mmanufactured by C. I. Hayes, Inc., of Cranston, R.I. The furnacetemperature is set to about 800° C., the treatment time is 4 hours, andthe atmosphere is helium flowing with a volumetric flow rate of about12,800 standard L/h (i.e., about 450 standard ft³/h, or equivalently,about 6.4 standard L/h.g). The treated activated carbon particles arecalled THe4-RGC, and their BET isotherm, mesopore volume distribution,and point of zero charge analyses are illustrated in FIGS. 1 b, 2 b, and3 b, respectively. Numerical values for BET, the sum of mesopore andmacropore volumes, point of zero charge, BRI/BLRI, VRI/VLRI, bulk oxygenpercentage by weight, and ORP are shown in Section VI.

IV. Exemplary Filters

Referring to FIG. 4, the construction of an exemplary filter will now bedescribed. The filter 20 comprises a housing 22 in the form of acylinder having an inlet 24 and an outlet 26. The housing 22 can beprovided in a variety of forms, shapes, sizes, and arrangementsdepending upon the intended use and desired performance of the filter20, as known in the art. For example, the filter 20 can be an axial flowfilter, wherein the inlet 24 and outlet 26 are disposed so that theliquid flows along the axis of the housing 22. Alternatively, the filter20 can be a radial flow filter wherein the inlet and outlet are arrangedso that the fluid (e.g., either a liquid, gas, or mixture thereof) flowsalong a radius of the housing 22. Either in axial or radial flowconfiguration, embodiments of filter 20 may be configured to accommodatea face area of at least about 0.5 in.² (3.2 cm²), in some embodiments atleast about 3 in.² (19.4 cm²), and in some embodiments at least about 5in.² (32.2 cm²), and a filter depth of at least about 0.125 in. (0.32cm), in some embodiments at least about 0.25 in. (0.64 cm), in someembodiments at least about 0.5 in. (1.27 cm), and in some embodiments atleast about 1.5 in. (3.81 cm). For radial flow filters, the filterlength may be at least 0.25 in. (0.64 cm), in some embodiments at leastabout 0.5 in. (1.27 cm), and in some embodiments at least about 1.5 in.(3.81 cm). Still further, embodiments of filter 20 can include bothaxial and radial flow sections.

The housing of embodiments of filter 20 may also be formed as part ofanother structure. While some embodiments of the filters areparticularly suited for use with water, it will be appreciated thatother fluids (e.g., air, gas, and mixtures of air and liquids) can beused. Thus, the filter 20 is intended to represent a generic liquidfilter or gas filter. The size, shape, spacing, alignment, andpositioning of the inlet 24 and outlet 26 can be selected, as known inthe art, to accommodate the flow rate and intended use of the filter 20.In some embodiments, the filter 20 is configured for use in residentialor commercial potable water applications, including, but not limited to,whole house filters, refrigerator filters, portable water units (e.g.,camping gear, such as water bottles), faucet-mount filters, under-sinkfilters, medical device filters, industrial filters, air filters, etc.Examples of filter configurations, potable water devices, consumerappliances, and other water filtration devices suitable for use with thepresent invention are disclosed in U.S. Pat. Nos. 5,527,451, 5,536,394,5,709,794, 5,882,507, 6,103,114, 4,969,996, 5,431,813, 6,214,224,5,957,034, 6,145,670, 6,120,685, and 6,241,899, the substances of whichare incorporated herein by reference. For potable water applications,embodiments of filter 20 may be configured to accommodate a flow rate ofless than about 8 L/min, or less than about 6 L/min, or between about 2L/min and about 4 L/min, and the filter may contain less than about 2 kgof filter material, or less than about 1 kg of filter material, or lessthan about 0.5 kg of filter material. Further, for potable waterapplications, embodiments of the filter 20 may be configured toaccommodate an average fluid residence time of at least about 3 s, insome embodiments at least about 5 s, in some embodiments at least about7 s, in some embodiments at least about 10 s, and in some embodiments atleast about 15 s. Still further, for potable water applications,embodiments of the filter 20 may be configured to accommodate a filtermaterial pore volume of at least about 0.4 cm³, in some embodiments atleast about 4 cm³, in some embodiments at least about 14 cm³, and insome embodiments at least about 25 cm³.

In some embodiments, the filter 20 may also comprise a filter material28 which may be used in combination with other filter systems includingreverse osmosis systems, ultra-violet light systems, ionic exchangesystems, electrolyzed water systems, and other water treatment systemsknown to those with skill in the art.

In other embodiments, the filter 20 may also comprise a filter material28, wherein the filter material 28 includes one or more filter particles(e.g., fibers, granules, etc.). One or more of the filter particles canbe mesoporous, mesoporous and basic, or mesoporous and basic and reducedoxygen and possess the characteristics previously discussed. Themesoporous; or mesoporous and basic; or mesoporous, basic and reducedoxygen activated carbon filter material 28 can be combined withparticles formed from other materials or combination of materials, suchas activated carbon powders, activated carbon granules, activated carbonfibers, zeolites, inorganics (including activated alumina, magnesia,diatomaceous earth, silica, mixed oxides, such as hydrotalcites, glass,etc.), cationic materials (including polymers such as polyaminoamides,polyethyleneimine, polyvinylamine, polydiallyldimethylammonium chloride,polydimethylamine-epichlorohydrin, polyhexamethylenebiguanide,poly-[2-(2-ethoxy)-ethoxyethlyl-guanidinium chloride which may be boundto fibers (including polyethylene, polypropylene, ethylene maleicanhydride copolymers, carbon, glass, etc.) and/or to irregularly shapedmaterials (including carbon, diatomaceous earth, sand, glass, clay,etc.), and mixtures thereof. Some examples of filter materials andcombinations of filter materials that mesoporous and basic activatedcarbon may be combined with are disclosed in U.S. Pat. Nos. 6,274,041,5,679,248, which are herein incorporated by reference, and U.S. patentapplication Ser. No. 09/628,632, which is herein incorporated byreference. As previously discussed, the filter material can be providedin either a loose or interconnected form (e.g., partially or whollybonded by a polymeric binder or other means to form an integralstructure).

The filter material may be used for different applications (e.g., use asa pre-filter or post-filter) by varying the size, shape, complexformations, charge, porosity, surface structure, functional groups, etc.of the filter particles as discussed above. The filter material may alsobe mixed with other materials, as just described, to suit it for aparticular use. Regardless of whether the filter material is mixed withother materials, it may be used as a loose bed, a block (including aco-extruded block as described in U.S. Pat. No. 5,679,248, which isherein incorporated by reference), and mixtures thereof. Examples ofmethods that might be used with the filter material include forming ablock filter made by ceramic-carbon mix (wherein the binding comes fromthe firing of the ceramic), using powder between non-wovens as describedin U.S. Pat. No. 6,077,588, which is herein incorporated by reference,using the green strength method as described in U.S. Pat. No. 5,928,588,which is herein incorporated by reference, activating the resin binderthat forms the block, which is herein incorporated by reference, or byusing a resistive heating method as described in PCT Application SerialNo. WO 98/43796.

V. Filter Examples Example 3 Filter Containing Mesoporous and BasicActivated Carbon Particles

About 18.3 g of Nuchar® RGC mesoporous and basic activated carbon powder(with D_(V,0.5) equal to about 45 μm) from MeadWestvaco Corp. ofCovington, Va., is mixed with about 7 g of Microthene® low-densitypolyethylene (LDPE) FN510-00 binder of Equistar Chemicals, Inc. ofCincinnati, Ohio, and about 2 g of Alusil® 70 aluminosilicate powderfrom Selecto, Inc., of Norcross, Ga. The mixed powders are then pouredinto a circular aluminum mold with about 3 in. (about 7.62 cm) internaldiameter and about 0.5 in. (about 1.27 cm) depth. The mold is closed andplaced in a heated press with platens kept at about 204° C. for 1 h.Then, the mold is allowed to cool to room temperature, opened, and theaxial flow filter is removed. The characteristics of the filter are:face area: about 45.6 cm²; filter depth: about 1.27 cm; filter totalvolume: about 58 mL; filter porosity (for pores greater than about 0.1μm): about 0.43; and filter material pore volume (for pores greater thanabout 0.1 μm): about 25 mL (as measured by mercury porosimetry). Thefilter is placed in the Teflon® housing described in the test proceduresbelow. When the flow rate is about 200 mL/min, the pressure drop of thisfilter is about 17 psi (about 1.2 bar, 0.12 MPa) for about the first2,000 filter pore volumes. Numerical values for F-BLR, F-VLR, η, and αare shown in Section VI.

Example 4 Filter Containing Microporous and Basic Activated CarbonParticles

About 26.2 g of coconut microporous and basic activated carbon powder(with D_(V,0.5) equal to about 92 μm) is mixed with 7 g of Microthene®low-density polyethylene (LDPE) FN510-00 binder of Equistar Chemicals,Inc. of Cincinnati, Ohio, and about 2 g of Alusil® 70 aluminosilicatepowder from Selecto, Inc., of Norcross, Ga. The mixed powders are thenpoured into a circular aluminum mold with about 3 in. (about 7.62 cm)internal diameter and about 0.5 in. (about 1.27 cm) depth. The mold isclosed and placed in a heated press with platens kept at about 204° C.for 1 h. Then, the mold is allowed to cool to room temperature, isopened, and the axial flow filter is removed. The characteristics of thefilter are: face area: about 45.6 cm²; filter depth: about 1.27 cm;filter total volume: about 58 mL; filter porosity (for pores greaterthan about 0.1 μm): about 0.44; and filter material pore volume (forpores greater than about 0.1 μm): about 25.5 mL (as measured by mercuryporosimetry). The filter is placed in the Teflon® housing described inthe test procedures below. When the flow rate is about 200 mL/min, thepressure drop of this filter is about 17 psi (about 1.2 bar, about 0.12MPa) for about the first 2,000 filter pore volumes. Numerical values forF-BLR, F-VLR, η, and α are shown in Section VI.

VI. Test and Calculation Procedures

The following test procedures are used to calculate the BET, point ofzero charge, BRI/BLRI, VRI/VLRI, bulk oxygen percentage by weight, ORP,F-BLR, and F-VLR values discussed herein. Also discussed herein arecalculation procedures for single-collector efficiency, filtercoefficient, average fluid residence time, and F-BLR.

While measurement of the BRI/BLRI and VRI/VLRI values is with respect toan aqueous medium, this is not intended to limit the ultimate use offilter materials. Accordingly, the filter materials can ultimately beused with other fluids as previously discussed even though the BRI/BLRIand VRI/VLRI values are calculated with respect to an aqueous medium.Further, the filter materials chosen below to illustrate use of the testprocedures are not intended to limit the scope of the manufacture and/orcomposition of the filter materials or to limit which filter materialsof the present invention can be evaluated using the test procedures.

BET Test Procedure

The BET specific surface area and pore volume distribution are measuredusing a nitrogen adsorption technique, such as that described in ASTM D4820-99, the substance of which is herein incorporated by reference, bymultipoint nitrogen adsorption, at about 77K with a Coulter SA3100Series Surface Area and Pore Size Analyzer manufactured by CoulterCorp., of Miami, Fla. This process can also provide the micropore,mesopore, and macropore volumes. For the TA4-CA-10 filter particles ofExample 1, the BET area is about 1,038 m²/g, micropore volume is about0.43 mL/g, and the sum of the mesopore and macropore volumes is about0.48 mL/g. For the THe4-RGC filter particles of Example 2, the BET areais about 2,031 m²/g, micropore volume is about 0.81 mL/g, and the sum ofthe mesopore and macropore volumes is about 0.68 mL/g. Note that therespective values of the starting materials CA-10 and RGC are: about1,309 m²/g; about 0.54 mL/g; about 0.67 mL/g; and about 1,745 m²/g;about 0.70 mL/g; about 0.61 mL/g, respectively. BET nitrogen isothermand the mesopore volume distribution for the filter material of Examples1 and 2 are illustrated in FIGS. 1 a and 1 b, respectively. As will beappreciated, other instrumentation can be substituted for the BETmeasurements as is known in the art.

Point of Zero Charge Test Procedure

About 0.010 M aqueous KCl solution is prepared from reagent grade KCland water that is freshly distilled under argon gas. The water used forthe distillation is deionized by a sequential reverse osmosis and ionexchange treatment. About 25.0 mL volume of the aqueous KCl solution istransferred into six, about 125 mL flasks, each fitted with a 24/40ground glass stopper. Microliter quantities of standardized aqueous HClor NaOH solutions are added to each flask so that the initial pH rangesbetween about 2 and about 12. The pH of each flask is then recordedusing an Orion model 420A pH meter with an Orion model 9107BN TriodeCombination pH/ATC electrode, manufactured by Thermo Orion Inc., ofBeverly, Mass., and is called “initial pH”. About 0.0750±0.0010 g ofactivated carbon particles are added to each of the six flasks, and theaqueous suspensions are stirred (at about 150 rpm) while stoppered forabout 24 hours at room temperature before recording the “final pH”. FIG.3 a shows the initial and final pH values for the experiments run withCA-10, and TA4-CA-10 activated carbon materials, and FIG. 3 b shows theinitial and final pH values for the experiments run with RGC andThe4-RGC activated carbon materials. The point of zero charge for theCA-10, TA4-CA-10, RGC, and THe4-RGC is about 5.0, about 9.7, about 8.8,and about 8.6, respectively. As will be appreciated, otherinstrumentation can be substituted for this test procedure as is knownin the art.

BRI/BLRI Test Procedure

A PB-900™ Programmable JarTester manufactured by Phipps & Bird, Inc., ofRichmomd, Va., with 2 or more Pyrex® glass beakers (depending on thenumbers of materials tested) is used. The diameter of the beakers isabout 11.4 cm (about 4.5″) and the height is about 15.3 cm (about 6″).Each beaker contains about 500 mL of dechlorinated, municipally-suppliedtap water contaminated with the E. coli microorganisms and a stirrerthat is rotated at about 60 rpm. The stirrers are stainless steelpaddles about 7.6 cm (about 3″) in length, about 2.54 cm (about 1″) inheight, and about 0.24 cm (about 3/32″) in thickness. The stirrers areplaced about 0.5 cm (about 3/16″) from the bottom of the beakers. Thefirst beaker contains no filter material and is used as a control, andthe other beakers contain sufficient quantity of the filter materials,having a Sauter mean diameter less than about 55 μm, so that the totalexternal geometric surface area of the materials in the beakers is about1400 cm². This Sauter mean diameter is achieved by a) sieving sampleswith broad size distribution and higher Sauter mean diameter or b)reducing the size of the filter particles (e.g., if the filter particlesare larger than about 55 μm or if the filter material is in anintegrated or bonded form) by any size-reducing techniques that are wellknown to those skilled in the art. For example, and by no way oflimitation, size-reducing techniques include crushing, grinding, andmilling. Equipment utilized for size reduction may include jaw crushers,gyratory crushers, roll crushers, shredders, heavy-duty impact mills,media mills, and fluid-energy mills, such as centrifugal jets, opposedjets or jets with anvils. The size reduction can be used on loose orbonded filter particles. Any biocidal coating on the filter particles orthe filter material should be removed before conducting this test.Alternatively, uncoated filter particles can be substituted for thistest.

Duplicate samples of water, each about 5 mL in volume, are collectedfrom each beaker for assay at various times after insertion of thefilter particles in the beakers until equilibrium is achieved in thebeakers that contain the filter particles. Typical sample times are:about 0, about 2, about 4 and about 6 hours. Other equipment can besubstituted as known in the art.

The E. coli bacteria used are the ATCC # 25922 (American Type CultureCollection, Rockville, Md.). The target E. coli concentration in thecontrol beaker is set to be about 3.7×10⁹ CFU/L. The E. coli assay canbe conducted using the membrane filter technique according to process #9222 of the 20^(th) edition of the “Standard Processes for theExamination of Water and Wastewater” published by the American PublicHealth Association (APHA), Washington, D.C., the substance of which isherein incorporated by reference. The limit of detection (LOD) is about1×10³ CFU/L.

Exemplary BRI/BLRI results for the filter materials of Examples 1 and 2are shown in FIG. 5 a and FIG. 5 b. The amount of the CA-10 mesoporousand acidic activated carbon material is about 0.75 g, and that of theTA40-CA-10 mesoporous, basic, and reduced-oxygen activated carbonmaterial is about 0.89 g. The amount of the RGC mesoporous and basicactivated carbon material is about 0.28 g, and that of the THe4-RGCmesoporous, basic, and reduced-oxygen activated carbon material is about0.33 g. All four amounts correspond to about 1,400 cm² external surfacearea. The E. coli concentration in the control beaker in FIG. 5 a isabout 3.7×10⁹ CFU/L, and that in FIG. 5 b is about 3.2×10⁹ CFU/L. The E.coli concentrations in the beakers containing the CA-10, TA4-CA-10, RGC,and THe4-RGC samples reach equilibrium in about 6 hours, and theirvalues are: about 2.1×10⁶ CFU/L, about 1.5×10⁴ CFU/L, about 3.4×10⁶CFU/L, and about 1.2×10⁶ CFU/L, respectively. Then, the respective BRIsare calculated as about 99.94%, about 99.9996%, about 99.91%, and about99.97%, and the respective BLRIs are calculated as about 3.2 log, about5.4 log, about 3.0 log, and about 3.5 log.

VRI/VLRI Test Procedure

The testing equipment and the procedure are the same as in BRI/BLRIprocedure. The first beaker contains no filter material and is used ascontrol, and the other beakers contain a sufficient quantity of thefilter materials, having a Sauter mean diameter less than about 55 μm,so that there is a total external geometric surface area of about 1400cm² in the beakers. Any biocidal coating on the filter particles or thefilter material should be removed before conducting this test.Alternatively, uncoated filter particles or filter material can besubstituted for this test.

The MS-2 bacteriophages used are the ATCC # 15597B from the AmericanType Culture Collection of Rockville, Md. The target MS-2 concentrationin the control beaker is set to be about 2.07×10⁹ PFU/L. The MS-2 can beassayed according to the procedure by C. J. Hurst, Appl. Environ.Microbiol., 60(9), 3462 (1994), the substance of which is hereinincorporated by reference. Other assays known in the art can besubstituted. The limit of detection (LOD) is about 1×10³ PFU/L.

Exemplary VRI/VLRI results for the filter materials of Examples 1 and 2are shown in FIG. 6 a and FIG. 6 b. The amount of the CA-10 mesoporousand acidic activated carbon material is about 0.75 g, and that of theTA40-CA-10 mesoporous, basic, and reduced-oxygen activated carbonmaterial is about 0.89 g. The amount of the RGC mesoporous and basicactivated carbon material is about 0.28 g, and that of the THe4-RGCmesoporous, basic, and reduced-oxygen activated carbon material is about0.33 g. All four amounts correspond to about 1,400 cm² external surfacearea. The MS-2 concentration in the control beaker in FIG. 6 a is about6.7×10⁷ PFU/L, and that in FIG. 6 b is about 8.0×10⁷ PFU/L. The MS-2concentrations in the beakers containing the CA-10, TA4-CA-10, RGC, andTHe4-RGC samples reach equilibrium in 6 hours, and their values areabout 4.1×10⁴ PFU/L, about 1×10³ PFU/L, about 3×10³ PFU/L, and less thanabout 1.0×10³ PFU/L (limit of detection), respectively. Then, therespective VRIs are calculated as about 99.94%, about 99.999%, about99.996%, and >about 99.999%, and the respective VLRIs are calculated asabout 3.2 log, about 5 log, about 4.4 log, and >about 5 log.

Bulk Oxygen Percentage by Weight Test Procedure

The bulk oxygen percentage by weight is measured using the PerkinElmerModel 240 Elemental Analyzer (Oxygen Modification; PerkinElmer, Inc.;Wellesley, Mass.). The technique is based on pyrolysis of the sample ina stream of helium at about 1000° C. over platinized carbon. The carbonsamples are dried overnight in a vacuum oven at about 100° C. As will beappreciated, other instrumentation can be substituted for this testprocedure as is known in the art. Exemplary bulk oxygen percentage byweight values for the filter materials CA-10, TA4-CA-10, RGC andTHe4-RGC are about 8.3%, about 1.1%, about 2.3%, and about 0.8%,respectively.

ORP Test Procedure

The ORP is measured using the platinum redox electrode Model 96-78-00from Orion Research, Inc. (Beverly, Mass.), and following the ASTMstandard D 1498-93. The procedure involves the suspension of about 0.2 gof carbon in about 80 mL of tap water, and reading the electrodereading, in mV, after about 5 min of gentle stirring. As will beappreciated, other instrumentation can be substituted for this testprocedure as is known in the art. Exemplary ORP values for the filtermaterials CA-10, TA4-CA-10, RGC and THe4-RGC are about 427 mV, about 285mV, about 317 mV, and about 310 mV, respectively.

F-BLR Test Procedure

The housings for the axial flow filters with mesoporous carbon are madefrom Teflon® and consist of 2 parts, i.e., a lid and a base. Both partshave an outside diameter of about 12.71 cm (about 5″) and insidediameter of about 7.623 cm (about 3″). The lid counter sets in the basewith an o-ring (about 3″ ID and about ⅛″ thickness) compression seal.The inlet and outlet hose barb connectors are threaded into the lid andbase with about 1/16″ NPT pipe threads. About ½″ thick by about 2¾″ ODstainless steel diverter (with about 3/16″ hole on the upstream side andabout 6 mesh screen on the downstream side) is counter set into the lidof the housing. The function of the diverter is to distribute the inletflow over the entire face of the filter. The lid and base of the housingengage such that a compression seal exists sealing the filter within thehousing. The lid and the base held together using four about ¼″fasteners.

The filter is mounted inside the housing and water contaminated withabout 1×10⁸ CFU/L E. coli flows through at a flow rate of about 200mL/min. The total amount of water flowing in can be about 2,000 filtermaterial pore volumes or more. The E. coli bacteria used are the ATCC #25922 (American Type Culture Collection, Rockville, Md.). The E. coliassay can be conducted using the membrane filter technique according toprocess # 9222 of the 20^(th) edition of the “Standard Processes for theExamination of Water and Wastewater” published by the American PublicHealth Association (APHA), Washington, D.C., the substance of which isherein incorporated by reference. Other assays known in the art can besubstituted (e.g. COLILERT®). The limit of detection (LOD) is about1×10² CFU/L when measured by the membrane filter technique, and about 10CFU/L when measured by the COLILERT® technique. Effluent water iscollected after the flow of about the first 2,000 filter material porevolumes, assayed to count the E. coli bacteria present, and the F-BLR iscalculated using the definition.

Exemplary results used to calculate F-BLR are shown in FIG. 7 a for theaxial flow filters of Example 3 and Example 4. The flow rate used inFIG. 7 a is about 200 mL/min and the influent concentration of E. colivaried between about 1×10⁸ and about 1×10⁹ CFU/L. The filters arechallenged with about 20 L once a week (every Tuesday) and the effluentwater is assayed as described above. The average fluid residence timefor the RGC filter is about 7.5 s, and that of the coconut filter isabout 7.65 s. The F-BLR of the RGC filter of Example 3 is calculated asabout 6.8 log. For the coconut filter of the Example 4 the collection ofthe effluent water is stopped at about 40 L (which is equivalent toabout 1,570 filter material pore volumes) as the filter shows almostcomplete breakthrough at that volume of water. The F-BLR is calculatedas about 1.9 log at about 1,570 filter material pore volumes.

F-VLR Test Procedure

The housings for the axial flow filters with mesoporous carbon are thesame as those described in the F-BLR procedure above. Water contaminatedwith about 1×10⁷ PFU/L MS-2 flows through a housing/filter system at aflowrate of about 200 mL/min. The total amount of water flowing in canbe about 2,000 filter material pore volumes or more. The MS-2bacteriophages used are the ATCC # 15597B (American Type CultureCollection, Rockville, Md.). The MS-2 assay can be conducted accordingto the procedure by C. J. Hurst, Appl. Environ. Microbiol., 60(9), 3462(1994), the substance of which is herein incorporated by reference.Other assays known in the art can be substituted. The limit of detection(LOD) is 1×10³ PFU/L. Effluent water is collected after the flow ofabout the first 2,000 filter material pore volumes, assayed to count theMS-2 bacteriophages present, and the F-VLR is calculated using thedefinition.

Exemplary results used to calculate F-VLR are shown in FIG. 7 b for theaxial flow filters of Example 3 and Example 4. The flowrate used in FIG.7 b is about 200 mL/min and the influent concentration of MS-2 variedaround about 1×10⁷ PFU/L. The filters are challenged with about 20 Lonce a week (every Tuesday) and the effluent water is assayed asdescribed above. The F-VLR of the RGC filter of Example 3 is calculatedas >about 4.2 log. For the coconut filter of the Example 4 thecollection of the effluent water is stopped at about 40 L (which isequivalent to about 1,570 filter material pore volumes) as the filtershows almost complete breakthrough at that volume of water. The F-BLR iscalculated as about 0.3 log at about 1,570 filter material pore volumes.

Calculation Procedures for Single-Collector Efficiency, FilterCoefficient, Average Fluid Residence Time, and F-BLR

The single-collector efficiency calculation for the filters usesEquation 4 and the dimensionless numbers described after that equation.Exemplary calculations for the axial flow RGC filter of Example 3 usingthe following parameters: ε=0.43, d_(m)=1 μm, d_(c)=45 μm, H=10⁻²⁰ J,ρ_(m)=1.058 g/mL, ρ_(f)=1.0 g/mL, μ=1 mPa·s, T=298 K, water flowrateQ=200 mL/min, filter diameter D=7.623 cm, and U=0.0007 m/s, giveη=0.01864. For the same parameters and for α=1, the filter coefficientis calculated according to Equation 2 as: λ=354.2 m⁻¹. Furthermore, theF-BLR of the same filter is calculated according to Equation 3 as about1.95 log. Similar exemplary calculations for the coconut filter ofExample 4, using the same parameters as above, give η=0.00717 and λ=65.5m⁻¹. Finally, the F-BLR of the same filter is calculated according toEquation 3 as about 0.36 log.

The present invention may additionally include information that willcommunicate to the consumer, by words and/or by pictures, that use ofcarbon filter particles and/or filter material of the present inventionwill provide benefits which include removal of microorganisms, and thisinformation may include the claim of superiority over other filterproducts. In one embodiment, the information may include that use of theinvention provides for reduced levels of nano-sized microorganisms.Accordingly, the use of packages in association with information thatwill communicate to the consumer, by words and or by pictures, that useof the invention will provide benefits such as potable, or more potablewater as discussed herein, is important. The information can include,e.g., advertising in all of the usual media, as well as statements andicons on the package, or the filter itself, to inform the consumer.

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference, the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention.

The embodiments described herein were chosen and described to providethe best illustration of the principles of the invention and itspractical application to thereby enable one of ordinary skill in the artto utilize the invention in various embodiments and with variousmodifications as are suited to the particular use contemplated. All suchmodifications and variations are within the scope of the invention asdetermined by the appended claims when interpreted in accordance withthe breadth to which they are fairly, legally and equitably entitled.

1. A method of providing potable water, comprising: (a) providing afilter comprising a housing having an inlet and an outlet and a filtermaterial disposed within the housing, the filter material formed atleast in part from a plurality of filter particles consisting ofmesoporous activated carbon, wherein: (i) a sum of mesopore andmacropore volumes of the filter particles is between about 0.2 mL/g andabout 2 mL/g; wherein mesopore means an intra-particle pore having adiameter between 2 nm and 50 nm, and macropore means an intra-particlepore having a diameter greater than 50 nm, (ii) a total pore volume ofthe filter particles is greater than about 0.4 mL/g and less than about3 mL/g, and (iii) a ratio of the sum of the mesopore and macroporevolumes to the total pore volume of the filter particles is greater thanabout 0.3; (b) passing water through the filter; and (c) removingbacteria and viruses from the water with the filter at a level of FilterBacteria Log Removal of greater than about 2 logs and a Filter VirusesLog Removal of greater than about 1 log.
 2. The method of claim 1,wherein the sum of the mesopore and the macropore volumes of theplurality of filter particles is greater than about 0.4 mL/g and lessthan about 1 mL/g.
 3. The method of claim 1, wherein the filter materialis disposed in the housing for axial flow and wherein the filtermaterial has a face area of at least 1.5 in.² and a filter depth of atleast 0.25 in.
 4. The method of claim 1, wherein the filter material isdisposed in the housing for radial flow, wherein the filter material hasan outside diameter of at least 0.5 in., an inside diameter of at least0.25 in., a filter depth of at least 0.125 in., and a length of at least0.5 in.
 5. The method of claim 1, wherein the step of passing waterthrough the filter material comprises an average fluid residence time ofat least 3 s.
 6. The method of claim 1, wherein the filter material hasa single-collector efficiency, η, of between about 0.005 and 0.25, and afilter coefficient, λ, between about 40 m⁻¹ and about 14,000 m⁻¹.
 7. Themethod of claim 1, further comprising a step of informing a user thatthe filter may be used to remove microorganisms.
 8. The method of claim1, wherein the filter material is further formed at least in part fromother materials selected from the group consisting of activated carbonpowders, activated carbon granules, activated carbon fibers, zeolites,activated alumina, activated magnesia, diatomaceous earth, activatedsilica, hydrotalcites, glass, cationic materials, polyethylene fibers,polypropylene fibers, ethylene maleic anhydride copolymer fibers, sand,clay, and mixtures thereof.
 9. The method of claim 1, wherein the totalpore volume of the filter particles is greater than about 0.4 mL/g andless than about 2 mL/g.
 10. The method of claim 1, wherein the porevolume is at least about 0.03 mL/g for pore diameters between about 4 nmand about 6 nm.
 11. The method of claim 1, wherein the step of removingthe bacteria and viruses from the water comprises removing bacteria andviruses with the filter at a level of Filter Bacteria Log Removal ofgreater than about 4 logs and a Filter Viruses Log Removal of greaterthan about 2 logs.
 12. The method of claim 11, wherein the step ofremoving the bacteria and viruses from the water comprises removingbacteria and viruses with the filter at a level of Filter Bacteria LogRemoval of greater than about 6 logs and a Filter Viruses Log Removal ofgreater than about 4 logs.
 13. The method of claim 1, wherein the filterhas a single-collector efficiency, η, of greater than about 0.002. 14.The method of claim 1, wherein the filter particles are wood-basedactivated carbon particles having a Brunauer, Emmet, and Teller (BET)specific surface area between about 1,000 m²/g and about 2,000 m²/g, thetotal pore volume is between about 0.8 mL/g and about 2 mL/g, and thesum of the mesopore and macropore volumes is between about 0.4 mL/g andabout 1.5 mL/g.
 15. A method for providing potable water, comprising:(a) providing a filter comprising a housing having an inlet and anoutlet and a filter material disposed within the housing, the filtermaterial formed at least in part from a plurality of filter particlesconsisting of mesoporous and basic activated carbon, wherein: (i) a sumof mesopore and macropore volumes of the filter particles is betweenabout 0.2 mL/g and about 2 mL/g; wherein mesopore means anintra-particle pore having a diameter between 2 nm and 50 nm, andmacropore means an intra-particle pore having a diameter greater than 50nm, (ii) a total pore volume of the filter particles is greater thanabout 0.4 mL/g and less than about 3 mL/g, and (iii) a ratio of the sumof the mesopore and macropore volumes to the total pore volume of thefilter particles is greater than about 0.3; (b) passing water throughthe filter; and (c) removing bacteria and viruses from the water withthe filter at a level of Filter Bacteria Log Removal of greater thanabout 2 logs and a Filter Viruses Log Removal of greater than about 1log.
 16. The method of claim 15, wherein the plurality of filterparticles has a point of zero charge between about 9 and about 12 and anOxidation Reduction Potential between about 290 mV and about 175 mV. 17.The method of claim 15, wherein the filter particles are wood-basedactivated carbon particles having a Brunauer, Emmet, and Teller (BET)specific surface area between about 1,000 m²/g and about 2,000 m²/g, thetotal pore volume is between about 0.8 mL/g and about 2 mL/g, and thesum of the mesopore and macropore volumes is between about 0.4 mL/g andabout 1.5 mL/g.
 18. The method of claim 15, wherein the plurality offilter particles has a point of zero charge greater than about 8, and anOxidation Reduction Potential less than about 400 mV.
 19. A method forproviding potable water, comprising: (a) providing a filter comprising ahousing having an inlet and an outlet and a filter material disposedwithin the housing, the filter material formed at least in part from aplurality of filter particles consisting of mesoporous, basic andreduced oxygen activated carbon, wherein: (i) a sum of mesopore andmacropore volumes of the filter particles is between about 0.2 mL/g andabout 2 mL/g; wherein mesopore means an intra-particle pore having adiameter between 2 nm and 50 nm, and macropore means an intra-particlepore having a diameter greater than 50 nm, (ii) a total pore volume ofthe filter particles is greater than about 0.4 mL/g and less than about3 mL/g, and (iii) a ratio of the sum of the mesopore and macroporevolumes to the total pore volume of the filter particles is greater thanabout 0.3; (b) passing water through the filter; and (c) removingbacteria and viruses from the water with the filter at a level of FilterBacteria Log Removal of greater than about 2 logs and a Filter VirusesLog Removal of greater than about 1 log.
 20. The method of claim 19,wherein the plurality of filter particles has a point of zero charge ofgreater than about 8, and an Oxidation Reduction Potential of less thanabout 325 mV.
 21. The method of claim 19, wherein the plurality offilter particles has a bulk oxygen percentage by weight of less thanabout 1.2%.